1. Field of the Invention
The present invention relates generally to a rotation stabilizing device in a microgravitational rotating apparatus performing experiments in a microgravitational state in space and more particularly to a rotation stabilizing device provided in the rotating apparatus so that vibration occurring in a rotating part may be suppressed by a vibration controller or a rotation stabilizer, such as a fin, provided in or on the rotating apparatus.
2. Description of the Prior Art
FIG. 39 is a schematic plan view showing one example of a rotating apparatus that is currently used in space. In FIG. 39, a rotating device 560, such as a motor, has four supporting members 561, 562, 563, 564 fitted thereto extending in horizontal directions. At ends of the supporting members 561 to 564, experimental boxes 570, 571, 572, 573 are fitted and experimental objects, such as plants, are contained in the experimental boxes 570 to 573. In the microgravitational state, such rotating apparatus is driven by the rotating device 560 to rotate at a slow speed of about 1 rotation/second and experiments on the objects in the experimental boxes 570 to 573 are carried out.
In the mentioned rotating apparatus, the experimental boxes 570 to 573 are fitted to the ends of the supporting members 561 to 564 so that the end portions thereof become large in shape. Also, while the rotating apparatus itself is symmetrical around the rotating axis, the experimental objects of different kinds and different sizes are contained in the experimental boxes 570 to 573 and there are caused weight imbalances between the experimental objects so contained. Hence, by the rotation, vibration occurs in a rotary shaft as well as in the supporting members 561 to 564 and the experimental boxes 570 to 573, thereby moving the experimental objects or giving bad influences thereto.
In the microgravitational state of space, when the experimental objects are placed in the experimental boxes of the microgravitational rotating apparatus as described above, and the experimental boxes are rotated so as to perform the experiments, vibration occurs in the rotary shaft due to imbalances between each of the experimental boxes. This vibration spreads to the surrounding environment via the rotary shaft and gives influences to the surrounding space equipment and apparatus as well as on the control thereof.
On the other hand, the applicant of the present invention has heretofore proposed another patent application relating to a magnetic bearing arranged in the rotating apparatus with a technology to control this magnetic bearing and thereby an efficient absorption of the mentioned vibration has become possible. The contents of this magnetic bearing will be described below.
FIGS. 37(a) to (c) show a microgravitational rotating apparatus for which a patent has been applied by the applicant, wherein FIG. 37(a) is a cross sectional side view, FIG. 37(b) is a a cross sectional view taken on line AH—AH and seen in the arrow direction of FIG. 37(a), and FIG. 37(c) is a cross sectional view taken on line AJ—AJ of FIG. 37(a). In the figures, numeral 10 designates a casing that contains an entirety of a rotator. On central portions of upper and lower surfaces of the casing 10, there are provided recess portions 10a, 10b projecting outwardly, and magnetic bearings 11, 12 are arranged in the upper and lower recess portions 10a, 10b, respectively.
The magnetic bearings 11, 12 have coils 1, 2 for an excitation purpose arranged on inner side surfaces of the recess portions 10a, 10b so as to form respective magnetic bearings. Numerals 3, 4 designate vibration sensors that are arranged on the inner sides of the coils 1, 2 within the recess portions 10a, 10b so as to function to detect displacement due to vibration of a rotary shaft 30, thereby controlling the displacement to suppress the vibration of the rotary shaft 30, as will be described later. The vibration sensors 3, 4, as shown in FIG. 37(c), are constructed by plural pieces thereof (four pieces in the illustration) arranged symmetrically on the inner side surfaces of the recess portions 10a, 10b so that vibration or displacement of the rotary shaft 30 on the ±X axis and ±Y axis may be detected. The rotary shaft 30 has its one end inserted into the recess portion 10a and the other end into the recess portion 10b so that the respective ends may be supported by the magnetic bearings 11, 12. The rotary shaft 30 is connected to a motor 13 within the recess portion 10b and is rotated by the motor 13 while being floatably supported by the magnetic force with a predetermined gap being maintained from the coils 1, 2. As seen in FIG. 37(b), the rotary shaft 30 has four arms 24, 25, 26, 27 fitted thereto extending horizontally in the directions of the X and Y axes. At ends of the arms 24 to 27, there are fitted box-like containers (hereinafter referred to as “the experimental boxes”) 20, 21, 22, 23.
In the above construction, the bearings of the rotary shaft 30 form the magnetic bearings 11, 12. The rotary shaft 30 makes no contact with the supporting portion of the casing 10 but is supported by the magnetic force. If vibration occurs in the rotary shaft 30, the vibration or displacement of the rotary shaft 30 is detected by the four vibration sensors 3, 4 arranged on the X and Y axes around both end portions of the rotary shaft 30. The vibration sensors 3, 4 detect variations caused by the vibration in the gap between the rotary shaft 30 and the sensors 3, 4 and input signals into a control unit, as described later. If the gap becomes smaller or larger, the control unit controls the electric current for the coils 1, 2 positioned correspondingly so that the gap may be returned to the original state, thereby actively controlling the vibration to be absorbed.
As to the construction of the coils 1, 2, for example, although illustration is omitted, wound wires of the four mutually independent coils are arranged so that the magnetic force may act in the four directions of the X and Y axes. When the rotary shaft 30 inclines to cause a displacement, excitation of the coil existing at the position where the displacement is largest and the variation in the gap relative to the coil is largest is controlled so that a repulsive force or attractive force acting on the rotary shaft 30 may be adjusted, thereby absorbing the displacement caused by the vibration.
FIG. 38 is a control diagram of the microgravitational rotating apparatus of FIG. 37. Vibration sensors 3a, 3b, 3c, 3d are those arranged around the upper end portion of the rotary shaft 30 and vibration sensors 4a, 4b, 4c, 4d are those arranged around the lower end portion of the rotary shaft 30. Each of the detected signals at these vibration sensors is inputted into a control unit 14. The control unit 14 drives the motor 13 to rotate the rotary shaft 30 and, at the same time, monitors the displacements, in the four directions of the X and Y axes, caused by the vibration of the rotary shaft ends and detected by the vibration sensors 3, 4. If the gap between the sensors and the rotary shaft becomes smaller or larger, the control unit 14 controls the excitation current of the wound wires of the coil existing at the corresponding position on the X and Y axes so that the repulsive force or the attractive force between that coil and the rotary shaft 30 is strengthened and the gap is returned to the original state.
In FIG. 38, numeral 15 designates a storage unit, in which pattern data of a demand value of an amplitude or an acceleration corresponding to the vibration frequency are stored in advance. The control unit 14, while monitoring the vibration of the rotary shaft 30 using the vibration sensors 3, 4, performs a comparison with the demand value. If displacement of the rotary shaft 30 occurs and the vibration becomes so large as to exceed the demand value, then the excitation current of the coil is controlled to absorb the vibration, so that the vibration of the rotary shaft 30 becomes less than the demand value. This control is carried out continuously. However, in the rotating apparatus of this kind, while the vibration occurring in the rotary shaft can be effectively controlled, such control is done only at the bearing portion and there is a limitation in the vibration control of the entire apparatus. Thus, a further improvement is being desired.
FIGS. 35(a) and (b) show another microgravitational rotating apparatus for which a patent has been applied by the applicant, wherein FIG. 35(a) is a cross sectional side view and FIG. 35(b) is a cross sectional view taken on line AF—AF and seen in the arrow direction of FIG. 35(a). In the figures, numeral 10 designates a casing that contains an entirety of a rotator. On central portions of upper and lower surfaces of the casing 10, there are provided recess portions 10a, 10b projecting outwardly and bearings 11, 12 are arranged in the upper and lower recess portions 10a, 10b, respectively. As the bearings 11, 12, any of magnetic bearings, spring-supported, or elastic- or plastic-material-supported bearings, air cushion bearings, spring or damper bearings and motor type or hydraulic type bearings can be employed.
Numeral 30 designates a rotary shaft that has its one end inserted into the recess portion 10a and the other end into the recess portion 10b. The rotary shaft 30 is supported at both ends or at one end thereof, according to the type of the bearings 11, 12, so that the rotary shaft 30 may make no contact with a stationary side of the casing 10. The rotary shaft 30 is connected to a motor 13 within the recess portion 10b. Numeral 435 designates an acceleration sensor that is fitted to an upper surface of each of experimental boxes 20, 21, 22, 23 so as to function to detect vibrations of the respective experimental boxes 20 to 23 and input signals into a control unit (not shown).
As seen in FIG. 35(b), the rotary shaft 30 has four arms 24, 25, 26, 27 fitted thereto extending horizontally in the directions of the X and Y axes and, at ends of the arms 24 to 27 and in front of the experimental boxes 20 to 23, there are provided upwardly and downwardly elongated box-like cases 428. In each of the cases 428, there are arranged a counterweight 481, pulleys 482, 483, a cable 484 and a motor 485. In this construction, the counterweight 481 is movable up and down and, while the experimental boxes 20 to 23 rotate, vibration caused by weight imbalances between each of the experimental boxes 20 to 23 can be absorbed, as will be described below.
In the rotator constructed as mentioned above, experimental objects of plants, animals, etc. are placed in the experimental boxes 20 to 23. In the space environment, the motor 13 is driven to rotate the experimental boxes 20 to 23 at a slow speed so that experiments to observe a growing state of the plants, a living state of the animals, etc. in space may be carried out. As various experimental objects having different shapes, sizes and weights are so contained in the experimental boxes 20 to 23, when they are rotated, there occur differences in the acceleration caused by the imbalances in the weight between each of the experimental boxes 20 to 23 and vibration occurs in the experimental boxes. This vibration is conveyed to the rotary shaft 30 via the arms 24 to 27 and further to the casing 10 via the bearing portions, thereby giving bad influences not only on the experiments but also on the surrounding environment.
Vibration caused in the rotary shaft 30 can be detected by the acceleration sensors 435. The vibration caused by the weight imbalances between each of the experimental boxes 20 to 23 is mainly of a mode to vibrate the experimental boxes 20 to 23 up and down at the ends of the arms 24 to 27 and this vibration is detected by each of the acceleration sensors 435. Signals from the acceleration sensors 435 are inputted into a control unit (not shown) and the control unit determines the experimental box in which vibration occurred. Then, in order to adjust the imbalance amount between each of the experimental boxes 20 to 23 that has caused the vibration, the control unit causes the counterweight 481 of the experimental box in which an upward acceleration is large to move downward and, reversely, causes the counterweight 481 of the experimental box in which a downward acceleration is large to move upward.
Thus, as mentioned above, if there are imbalances between each of the experimental boxes 20 to 23 and vibration is thereby caused during the rotation, imbalances in the acceleration caused by the imbalance amount during the rotation are adjusted by upward and downward movements of the counterweights 481 and, by this adjustment, the upward and downward vibration of the experimental boxes 20 to 23 caused by the imbalances can be prevented.
FIGS. 36(a) and (b) show another example of a microgravitational rotating apparatus that is related to the apparatus of FIGS. 35(a) and (b), wherein FIG. 36(a) is a cross section side view and FIG. 36(b) is a cross section view taken on line AG—AG and seen in the arrow direction of FIG. 36(a). This example is constructed such that a pair of counterweights are arranged on upper and lower sides of each arm and imbalances caused between each of the experimental boxes are resolved by moving the counterweights in the horizontal direction so that vibration caused by the imbalances may be suppressed. Construction of other portions of this rotating experimental apparatus is the same as that of the apparatus of FIGS. 35(a) and (b).
In FIGS. 36(a) and (b), on the upper side of each of the arms 24, 25, 26, 27 and in parallel therewith, there is arranged a threaded bar 436a. Each of the threaded bars 436a has its one end connected to the respective experimental boxes 20 to 23 and the other end connected to a motor 431a that is fixed to an upper surface of each of the arms 24 to 27. A counterweight 429a is fitted to each of the threaded bars 436a via a thread engagement and, when the motor 431a rotates to thereby rotate the threaded bar 436a, the counterweight 429a moves rightward or leftward in the figures. Likewise, on the lower side of each of the arms 24 to 27 and in parallel therewith, there is arranged a threaded bar 436b to rotate between a motor 431b and the respective experimental boxes 20 to 23 and thereby a counterweight 429b moves rightward or leftward in the figures. Also, an acceleration sensor 435 is fitted to an upper surface of each of the experimental boxes 20 to 23.
In the construction in which there are provided the four arms 24 to 27, as shown in FIG. 36(b), and the counterweights 429a, 429b are arranged on the upper and lower sides of each of the arms 24 to 27 so as to move horizontally, when weight imbalances occur between each of the experimental boxes 20 to 23 and vibration arises due to differences in acceleration during the rotation, signals from the acceleration sensors 435 are sent to a control unit (not shown). Thereby, each of the motors 431a, 431b, which amount to eight in total, is controlled to move each of the counterweights 429a, 429b rightward or leftward so that the imbalances may be resolved. Thus, the vibration caused by the imbalances in the weight can be suppressed.
In the microgravitational rotating apparatus shown in FIGS. 35 to 38 and described as above, while the vibration caused in the rotating apparatus during the rotation can be absorbed within the casing 10, a complete absorption is not always possible according to the kinds of the vibration and a more accurate vibration control has been desired.
Also, in the abovementioned microgravitational rotating apparatus, foreign matters are liable to encroach into the bearing portions during the rotation and there is considered a case where the rotary shaft may stop suddenly. Following such a sudden stop of the rotary shaft, the experimental boxes also stop, and this gives shocks not only to the experimental boxes but also to the experimental objects contained therein. Also, a sudden vibration occurs following the sudden stop and this gives bad influences to the surrounding environment.